Process of firing porcelain.



FATBNTBDJAN. a, 1907.

0'.- ELLIS., PROCESS 0F PIRING PORCELAIN.

APPLICATION FILED JANA, 1906.

FIG l l/l//l l `miXtures moreof the nature of glassd-a're practice and use thefsame. l

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UNITED vstrAims .iunlriaivrl onirica.

oARLnToN' ELLIS', or `wn'rrr; PLAINS, 4'NEW YRK.I

i No. 840,559'.l lSpe'ication of To all whom it may concern.;y

Be it known thatl,` CARLTON ELLIS, av citizen of the United Stat'es,.resi inWhte Plains, countyfof Westchester, 'an lState"V of New York,l have invented certain new and useful Improvements in Processes of Firing Porcelain; and I yhereby declare 'the followingl to be afull, clear, and exact `description of the invention, such asf will enable *othersl skilled vin the art to `vwhich it iappertains to 4This invention relates-to a processof firing .porcelain and similar. ware and it consists in amethod of heatin porcelain, terra-cotta, glass, and lire-set p astics generally, in the manufacture and inthe decoration thereof,

.by means ofignitedatmos heresof certain eculiar characteristic-,s, a as ,more fully hereinafter set 'forth-matters of .novelty beingparticularly pointed out in the appended claims." ,Y A

Porcelain-ware, terra-cotta, and wareof'. the many modernre-setplastic compositions 'which ran e. between thel true'A porce- ,customarily fired in mulilescr saggars, partly with theidea of avoiding'idirect contact, in'so far aSjmayzbe, with fire-gases'fand' 'partly toavoid injury from; ash aparticles; sot, ac.v

. Subsequent ringvof lsuch@[articles to affix glazes or decorations, as inchinap'ainting, iegv also done in the 'same 'way-1 The comp ete exclusion of fire-gases, however, 'is not prac.- ticable', since at the vhigh'.ten 1peratur es' emf ployed alLmateria'ls' are more or :less permetable, by gases, even Aifthey b e nonporous,

while asv a' matter .of fact thenrefractory clays .and compositions Aused forfmuflles and sa'g.

' arsare alwaysporousiand ssured and a f` ord ready passa esways for gases, which un# Y der the ordinary aWsof diffusion constantly tend- :to lavera ethe .pomposition Aof the atmospheres and withoutthe vI Iulle or Sa, 3,1, t v: n modern4 ractice, moreover, :where por-v celain', stoneware,;andterracotta are made on the largescale, in order to permit cheap manufacture of inutiles of the necessary size, itis the custom to makethem sectional-to build them' up of; segments;-

lnring, j-thesesegments natrii'allyY expand. :and contract,

producing fissures prpenings; Thesefcrevi "ices, together 'with-the naturaporosity of the.

`materalsfromyviiichtl-1e'mu e l p 'mitaiready' interchange of thegases .within ifmade', per- 'Application filed January 4., 19t-)6. Serial'No.'2l94, 513.

Patented Jan. 8, 1907.

'Letters raten@ f I- and without the muflie'lhe smaller saggars,pin which valuable porcelain, &c., articlesare fired, while'not so apt to crack or fissure, are nevertheless quite as ermeable to ases, because the necessary'c osures'never ring, this gas permeability of the muflies and saggars 1s a source of grave inconvenience and loss; Withgases of a reducing nature,

from ordinary fires or from ordinary gas there is always danger of free carbon gaining saggar, in the latter case through the decomt accurately. With the usual methods of 6s such as those often obtained in the ames access to` or'beingformed within the muflieor lposition` of hydrocarbons or by the reaction 'of free hydrogen on carbon oxids, both these reactions being very much facilitated by the like lead oXid, are oftencontained in glazingl `compositions it'frequently happens that arecause of its 'rect effectI on the Ware.'- other cases of course a reduc' atmosphere is sometimes desirable as in riiiiiug the copper-reds in decorating china and glass. Free carbon, however, is always detrimental. It is obvious that ability to contreljthe atmosphere in the muile is highly desirable.v

prior history of 4the art toobviate the stated inconveniences due tothe ordinary methods "of rin form o? an effort to exclude'fire-gas'es from the interior of muflies or saggars. This is, however, wholly impossible practically, and moreover, the more impermeable the' mule or `4saggar has been... made the slower has proved the transmission of 'heat through its through materials 4of the nature .o those which must be used for muiiles and saggars.

factthat, the material'being heated, the clay, or the iron, oxids therein contained act as a and salts. used. china: ainting are readily reducible and since reuciblecompounds,

ducing atmos here is 'also detrimental, -be-` Many attempts -have been .made in theu but these have generally taken the IOO walls. Transmission of 4heat is alwa s slow 1 1o and very slight thickening of their walls, as in efforts to make them impermeable, retards such transmission very much. Further, the heating in the muffle really depends lin `a measure `on interchange of gases through the walls. Again, evenness of heat is a prime necessity in firing ceramic wares of all kinds,

but particularly with such iire-set plastics as are now used in modern art potteri'es. Frequently with these latter compositions there is a comparatively narrow range of de grees between the point where the ware is baked.. fritted, or vitrified and that at which .it'fuses down wholly or partially. The same is true in making stoneware and in glazing and decorating all kinds of ceramics. Obviously it is desirable that about the same degree of heat shall obtain in all parts of the muiiie or sagga-r containing a piece of such ware, since otherwise one portion 'may' be melted and another not completely baked or formly save by a iaming fire, by the burning of gases containing enough free carbon to permit the expansion of flame around the en tire surface of the muflie, and the development of heat atall points by radiation from the suspended carbon. This is, however, a sooting- Yss dame-and dangerous to the contents of the muffle for reasons stated, and, moreover, evenwith the best regulable of such flamesaslthat from an oil-burner, for instancedi 'rect observation will show the difficulty of getting the same developmentof heat. at all pointsso that the floor of the muffle shall be neither hotter nor cooler V`'than the walls ,or the roof. Such a flame is usually more or less stratified; but the danger of such a sooty flame, though it permits of evener heating than any other prior method of firing, has led to its disuse except for ,the coarsest articles. In practice it is usually sought to have conn plete combustion lof' the iame heating the muffle without the development of free carbon or a reducing atmosphere; but no ordinary flame is of suflicient volume to completely bathe a large mufiie, and, furthermore, the zoned character of such a llame necessarily leads to differential development of heat at di'lferentpoints where it impinges.

. Ordinary fuels are, so to speak, too concentrated. They give a .relatively short hot flame,v and froriheating objects of large vol ume, such as a muflie, reliance must necessarily be placed on the sensible heat of the products of combustion; but sensible heat is given upto the'first cooler objects encountered, and the result is that in such a manner 4of heating in a given space, as the flamechamber surrounding a muiiie, temperatures rapidly decrease from the hottest point in such a short flame or the oxidizin zone thereofand the surfaces immediate y adjacent thereto to points more remote. Unevenness of heating in the space is of course the. result. With such a large object to be heated as aporeclain muifle thls unevenness is very apparent, some one wall being always much hotter than the others. This is very detrimental to ware in such a muii'le, causing glazes to iiow and fluxuinevenly, causin unevenness in baking, &c. lt is also retrimental torthe muffle itself, causing it to crack and be short-lived. The defects mentioned are inevitable and inherent in all the fuels heretofore tried used for heating porcelain muiles. -They all give rise to too much heat in one portion of the Haine-chamber containing the muflie and to too little in others, and they give no sufficient control over the character of the atmosphere in the muifle itself. Therefore manufacturers of porcelain and similar ceramic wares and producers of decorated china and glass have been forced to accept the production of a large percentage of waste and culls as unavoidable, `and such i articles arenecessarily relatively high-priced for this reason. t

It is the obj ect of this invention to` obviate these inconveniences and losses by a sim le, cheap, and practicable method. Instea 'of striving to prevent the entry of fire-gases into lOO muffles and saggars these gases are simply made of such nature that their entry can do no harm, or will be advantageous, thereby enabling the use of thinner more readily conducting walls in mufiies and saggars, with the result of longer life and cheaper operattion, as well as cheaper construction. Simultaneously such gases are made of a nature permitting as tardy a burning as may be desired, thereby enabling the production of `a flame which may at pleasure be caused to have any desired volume or temperature and be caused to envelop a muiile or saggar completely, burning uniformly and developing heat uniformly at all points. In this method no reliance need be placed on the conveyance .of heat, as sensible heat in the products of combustion. It is developed at the point where it is required. The advantage of these ence 'of free carbon there is no particular ob' ject in endeavoring to restrain its contacting .with the articles to befired by permeating the munie-walls. Such kentry is even tobe desired in many cases as facilitating heating and influencing the production of special results in glazing and coloring. In such cases 1t 1s generally an oxidizing character -whichis desired, as in the use ofleadand other oxids and metallic salts in glazes and paints; but in somecases, as in the production of avanturin finishes, it` is Vdesirable -t o.- have it reducing,

. facility.

Either character can be produced withv equal Briefly stated, my'process consistsin ad mixing Wit-h the gases, to furnish the flame atmosphere around the muflie, regulated amounts of d iluent gases. Where oxidizing atmospheres are desired, this diluent may he air in vexcess of the amount required for combustion but generally I prefer to use roducts of combustion, because ofthe speci c retarding influ'ence of the carbon dioxid thereinv contained. "Thereby Iscure a tardily-burning mixture which gives' an inflated flame of any desired volume and which, While yield# ing .no less total heat than thecombustible component alone, yields it over a greater Varea tion is and in a longer time. develop an even' generation of heat overthe entire surface ofthe muffle., The retardapartly due to thedilution, partly due to the s ance with the ordinarylaws of mass action.-

` The net result is a flame which may be made of any volumefof Lany'ftmperature, and-fof any s eed of and which may be. ad- .4o

juste in anyone of these respects hy a sim-fA ple adjustmentof'the proportions of its com,

ponent ases. Suha'flame or flame atmos here wlllenvelop the muiieor saggar to 'be' eated, burning evenly;and,homogeneously` at all points and ldeveloping its lheat at the point where itis wanted' instead of some-- whereelse. Thereby I attain the result long sought in this art of aneven muffle-heating;

In order to assure the greatestpossible uniformity, however, Il preferably, though .not

necessaril make the gas mixture 'so dilute and tardi y-burning as to .re une the heat of the heat zone of the flamec amber forrned by the rnuflle and the encompassing-chamberv walls of the furnace, to complete its combustion.

will insurean e ua combustion throughout,

i and consequent y an equal ldevelopment of heat at all points.

In ,the gas mixture used, whether it 1s to furnish a flamef'atmosphere of oxidizing or.

4 'reducing nature, I proportion the components so that no free carbon shall be devel-A v oped; By this means permeation of the atis. s

In vthis manner I can owing action ofthe c-arbondioxid 'of the Iproductsof .combustion which retardsthe. formation of more lcarbon dioxid'in-v accord- Such a mixture maybe 'readily'made, In afproperlydesi ned flamec'hamber this the gas, and some steam is inevitably found in the gas whatever precautions may be taken.l Steam' in the gas, presentl from whatever cause, and the steam formed in burning hydrogen act detrimentally, since the' violent reversible reactions with carbon oxids change derange the normal development of the flame, deadening it, and some of such reactions may occur in the mufHe, even producing .free carbon therein, with resultant sooting of the ware. I therefore prefer to' operatea gas-producer With'products of comoccurring .whenever temperatures' bustion as anendothermic or cooling agent, thereby producing a gas substantially dryer Y free from hydrogen or steam. Water-.gas may, however, bevused; but its employment necessitates more care and attention on the part'of the operator. I may also, where con venient,use such .rich gases as natural gas; but in such cases I prefer to take special pre; cautions. With natural gas, in order to ob'- 'vi-ate the possibility of the, formation` of free .carbon or fany local reducing action,- thegdiluting-gas is usefully composed of 'a large excess of air-over that necessary 'for complete l vcon`1bustion, admixed, as usual, with more or less' products .of combustion. A mixture of l.natural gas with a large excess of air over that' necessary for complete combustion can IOO "be made to V-burn at anyrate desired, and the flame is naturally stronglyoxidizing. With very 'large'. excesses such a mixture willjonlgfv burnin a heated chamber suchas describe IIO .The gas-may be taken from theproducer or other source and admixed directly with v the necessaryfdiluents, and air'and .themixture sent finte the flame? chamber,.or the desired mixture may also, .and .very simply, be, so to speak, formed "in lace by b urni fuel on a grate v vitha-fo'ice y.idraftof airan i. l

products ofcombustionrdelitered throu' 4hitfat lsuchga rate 'that' more: orless of bot `go` through unchanged andmix with the carbon y monoxid formed from the fuel. The carbon dioxid inthe draft-current prevents the for#` mation of carbony dioxid .on the grate, andl the fire therefore lruns cool .and furnishes `a `maximum of 4'carbon' monoxid. :In either 'method of making the mixture 1t is obvious E that'a 'simple change of a valve or two, regulati the feed of one component or the other, icient to adjust the composition of the llame atmosphere in the iamechamber, making its combustion slow or as rapid as may be desired and causing the atmosphere within or without the muffle to be that best adapted to the particular end sought.

' With the regulablenon-sooting-lame at vmospheresl described the main function. of

the muilie or saggar is to serve as a shield to protect the ware from mechanical contamination by flying dust, ashes, and cinders instead of being, yas heretofore, also designed v as a shield against llame-gases.

the slow-burning gas mixture, but, because of ,its small diameter and the fact that the said gases come into actual contact with the catalytically-acting clay particles ofthe pore, the action of the por is much more rapid.

With very dilute flame-atmospheres it is desirable to use hot air as a component of the Amixture or as a burning agent, and this may be'usefully obtained by regenerators or other devices abstracting heat from the waste gases leaving the flame-chamber.

in the accompanying illustration I have shown more or less dia rammatically one type of apparatus' suitab ve for carrying out ly process selected from the wide variety of structures which-may be used.

Figure 1 isa central vertical section, partly in elevation, showing a Cplurality of inutiles and heating devices; an Fig.` 2 is a-partial horizontal section. y

Like reference characters designate like partsin both views.

Characters 1 1- design-ate a porcelain muflle inclosed b a hoodin -furnace 2, with 4.the comparative y narrow ame passage or chamber therebetween and provided with a plurality of gra-tes 3, with fuel-feeding doors 4.

` 5 is a downtake-chamber in the center, continued as flue 5 to chimney-stack 6.

From the stack pipe 7, provided with valve 8, abstracts a controllable amount of products of combustion. Pipei) and valve 1() supply a controlled amount of air for adlmixture therewith under the suction of fan desired. This arrangement enables the formation of the desired flame atmospheres from solid fuel in a convenient manner. Ordinarily in this method of working the fuel will be maintained in a shallow bed; but if so desired the grate 3 may be run as a straight gasproducerl by supplying a bed of fuel thereto deep enough to insure complete reaction with the draft-current sent through.

In such cases the air necessary for combustion and the products of combustion for dilution may. be admixed at the bottom of lame-fiue 15 by means of pipe 18, provided with valve 19.

When gaseous fuel is to be used, no fuel is placed on the grate, and gas more or less diuted is supplied through pipe 17, which is rovided with valve 16, adjacent to the openmg of the twyer 14, or the mixture may be prepared by introducing into pipe 7 on the suction side of fan 12 a su pl f of gas through pipe 11.rk With the highly-diluted gas mixtures used 'in the present process llame will not propagate back of the heated zone of flue 15. ln this fiue, owing to its comparatively small cross-section, the gases are very thol-,

oughly mixed by eddy-currents and a uniform tardy burning flame fills the whol-e flue.

Combustion is inaugurated in the flue 15 and continued and completed in downtake 5, combustion being substantially uniform throughout. shown there is a slight fan-pressure in the narrow flue 1 5 and chinmey-draft in downtake 5, there vwill be more or less drift of gases through the porous walls of the muflle, this taking place to the largest extent at the bottorn of the mulile, where the difference in pressure is the greatest; but no burning will take place in the muffle itself, the reaction of the gases on eachother being completed in the assage through the glowing walll This tentibs to keep the point 1n the muffle opposite the gas-entrance as warm as the rest, and the entry of hot gases at the foot of the muiiie tends materially toward equalizing temperatures in the muflleitself. Naturally if in the gas mixture used there is an excess of oxygen over that required by the combustible the inward-drifting gases are oxidizing. If the combustible is in excess, they are reducing. Where, as is preferred, a dry combustible gas, free of water, hydrogen, and unoxidized carbonis used, there need be no fear of sooting.

1. The process of firing ceramic ware which consisis in placing such ware within a suitable in closing chamber and aq'iplying heat by circulating around such chamber a body oll burning gases free from unoxidizcd carbon., The combusi ion in such gas body occurring in substantially the entire portionv of such body which is in ibo vicinity of such chamber.

lnasinuch as in the structure TIO . 55 the Ware being burned.

2. Thev process of firing"ceramic Ware ,i which consists in placing y such Ware Within a suitable inclosing chamber and applying heat by circulating'around such cham er a body of, burning gases vfree from unoxidized car-l -b'on and comprising a mixture'ofcombustible gas, oxygen, and combustion-.retarding gas, the combustion'in suc gas body occurvring-in substantially the entire portion' of such [c body which is in the vicinity of such chamber. 3.` The process of firing ceramic Ware' whichfconsists in placing suchWare Within a suitable inclosing chamber andapplying heat by circulating around such cham er a body l5 of burning gases free from unoxidizudcarbon and com rising afmixtpre of combustible gas,'com ustion-ret'ardlng gas, and an excess of oxygen, the combustion. in such gas body occurring in substantially the entireV portion of such body Which is in the vicinity of such chamber. 1 4. The process of ring ceramic ware which consists in placing such Ware within av suitable inclosing chamber surrounded by a combustion space having heat radiating walls, and circulating through such combustion-s ace.a body of burning gases free from unoxiized carbon, combustion insuch gas body occurring substantially throughout the 3c portion of such chamber. b

5. The process vof firing ceramic Ware which consists in placing-such Warewithin `a suitable inclosing chambcrsurrounded by a 3 5 combustion space y having heat radiating Walls, and circulating through: such combustion-space a body-of burning gases free from freecarbon and comprising a mixture of'combustible gas, oxygen, and combustion-re1 4o tarding-v gas, combustionin such gas body occurring substantially throughout the portion vof such body which is in the vicinity of such chamber. i I

. 6. The process of ceramic. Ware Whichconsists in placing such ware within -al space separated fronti a combustion-space bya porous heat-radiating wall'; and circulating throughgsuch=- combustion-space a body of burning gases free from'unoxidized carb on'and 5o comprising a mixture of combustible gas, oxygen, andcombustion-retarding gas, combustion in such gas body occurring in substantially the entire portionof -such body which is in said4 combustion-space in the vicinity of 7. The process of firing ceramic lWare which consistsin placing such Ware Withinfa space separated from a combustion-spacefby a porous heat-radiating Wall, and circulating 6o through such combustion-space a. body of burn-ing gases' free from unoxidizedA carbon,

combustion in such gas body occurring in substantially the entire portion of such body which is inthe vicinity of the `Ware being v/burned.

.drift of such gases through such porous wall into said chamber, and by the catalytic accompletin -Walls, circulating through such combustion- 8. The process of firing ceramic Ware which consists in placing such Ware Within a suitable inclosing chamber having a porous Wall composed of vrefractory material, cinculatn past said ,Wall a body of burning gases 7c free "omunoxidized carbon and producing a drift of such gases through such porous Wall Tinto said chamber, and by the catalytic action of the material of such wall completing the' combustion of the gas passing therethrough prior to contact With the Ware.

-9. The process Aof iring ceramic Ware which consists inv placing such Ware Within a suitable inclosing chamber having a porous wall composed of refractory material, circulating past such Wall abody of burning gases free from unoxidized carbon and comprisin a mixture of combustible gas,4 oxygen, an combustion-retarding 1 gas and producing a tion of the materiall of such'wall'completing the combustion of the gas assing therethrough prior to' contact with tV e Ware.

10. The process of firing. ceramic Ware which consists in passing such Ware Withina suitable inclosing chamber having a porous Wall composed of refractory material, circul p latin past such Wall a body of burning gases of such body which is in the vicinityl fr ee om unoxidized carbon and comprising a mixture of combustible gas', combustionretarding gas, and an excess of oxygen and producing a driftof such gases` through such j porous Wall intQ-said chamber, and by the` catalytic action of the materialof such Wall the` combustion of the gas passing theret vrough prior to contact with the ware., l Y

4 11. The process of iiring ceramic Ware which consists in placin such Ware Withina suitable inclosing chamber surrounded by a, .combustion-chamber andl separated therefrom by .a refractory Wall, said combustionchamber having refractory heat yradiating IOO I I O chamber a body of burning gases free from unoxidized carbon and comprising .a mixture of combustible and combustion-supporting gases too poor in combustible to burn eXce t. under the influence'of heat radiated from t e walls of said chamber, and by the action of such radiated heat burning said gases, the combustion in such gas body occ in substantially .the entire portion of such body which is inthe vicinity of said `Erst-mentioned chamber. g 12. The process of firing, ceramic WareI which consists in placi such ware Within a suitable inclosi cham er, passing throu h a porous body o refractory material a bo of (gas comprising a mixture of combustible an :combustion-supporting gases free from unoxidized carbon and too'poor to burn except-under the influence of heat radiated from surrounding objects, by the heat of the 13;)

IIS

said body of refractory material completely burning the combustible constituent of such gas body7 and causing theproductsof combustion to pass over the Ware to be burned.

13. rlhe process of ring ceramic Ware which consists in placing such Ware Within an' inclosing chamber surrounded by a combustion-space and circulating through Vsuch space a body of-bi1rning gases free from unox'idized carbon and maintaining around such chamber a zone of approximately uniform temperature by maintaining approximately uniform combustion of such gases in y all portions of such combustion-space in the immediate vicinity of such chamber. 14. 'The process of firing ceramic ware which consists in placing such ware 4within an inclosing chamber surrounded by a combustion-space and circulating through such space a body of burning gases free from unoxidized carbon and comprising a mixture of' combustible gas, oxygen, andcombustioin retarding gas, and maintaining around such chamber a zone of approximately uniform temperature by/regulating the pro} )ortion of combustion-retard1ng gas in the mixture so as to producevapproximately uniform comoustion of such gases in all portions of suchcombustion-space in the immediate vicinity of such chamber.'

In testimony whereof I aliix my signature -in the presence of two witnesses.

CARLETON ELLI"4 Witnesses:

FLETCHER P. SCOEIELD, T. H. FAIR. 

